The overlord becomes stationary and generates creep in a 2×2 area below it. Moving the overlord cancels this ability.

Mutate Ventral Sacs (Requires Evolution Chamber)

Allows a morphed overlord to carry 8 cargo space worth of units

Spawn Changling (50 Energy)

Overseer spawns a changling for 150 seconds. Changelings are controlled units which change into the basic army unit of your enemy when it walks into enemy vision. It does not have an attack and is killed by any attack.

Contaminate

Overseer disables an enemy structure for 30s. The structure is unable to research upgrades or build units.

Sight: 11 Range

Overlord Speed: 0.82 (2.63)

Overseer Speed: 2.62 (4.72)

Tags

Overlord: Armored, Biological

Overseer: Armored, Biological, Detector

Strengths

Overlords are much more than just a way to gain maximum supply. They are incredibly important units in the early game for scouting what your opponent is doing. They have utility once you can morph ventral sacs to drop banelings or units. Overseers are essentially just a faster overlord with more utility in scouting due to the spawn changling ability.

The first overlords that you make are generally best sent out to scout your opponent and find what build they are using. Overlords are also integral to builds such as Dark’s ravager ling queen timing in ZvT due to being able to transport Queens to the Terran base.

Weaknesses

There are some weaknesses to overlords, if one overlord is sniped in the early game by a marine, queen or stalker the game can snowball in your opponents favor, especially if you become supply blocked for a significant amount of time. To avoid this, there are many doodads and high ground areas on most maps where you can hold position your overlords so that marines/stalkers/queens don’t have vision and can’t attack your overlord.

Further Analysis

The utility of overlords mostly comes from being able to transport units similarly to medivacs or warp prisms.

There have been many uses of drop overlords in professional play. The first and biggest event where drop overlords had a significant impact was the beginning of 2016 when Dark revolutionized the Zerg vs Protoss Match-up when he played against stats for first place at SSL.

Today they are still used for baneling drops, primarily against Protoss and Terran players. Dark has also begun to use drop overlords to carry queens for a timing attack in the Protoss and Terran match-ups.